Checking a BC548B NPN Transistor?

[Meat Plow]

Thanks to everyone who has replied. I am really struggling as you can see.
I can't believe that all my new BC548B transistors are broken.

Does this seem correct?

C = 4.98V
B = 1183mV

With E emitting 615mV

Does not appear to amplifying anything to me? What could I have done wrong?

TIA

The only diode check type conduction in a bipolar transistor should be
between the base and emitter. What exactly is a BC548B? If you want
leakage checks you need something you can plug all three leads into like
my Sencore Cricket.

 

[Marra]

Nip down to Maplin and get a meter with a transistor tester.

While a normal meter can test go or no go it cant test HFE problems.

 

[John Fields]

Nip down to Maplin and get a meter with a transistor tester.

While a normal meter can test go or no go it cant test HFE problems.

---
Sure it can. (View in Courier):


1.

+V>-+-----+-------+
| | |
[1M]<--+ [AMMETER]
| |
| C
+-----------B
E
|
GND>--------------+


Starting with the pot cranked to maximum resistance, rotate it so
that some convenient current (Ic) is displayed by the ammeter then,
without disturbing the setting of the pot, disconnect the meter from
the collector, place it in series with the base, and connect the
collector to +V:


+V>-+-----+-------+
| | |
[1M]<--+ |
| |
| C
+-[AMMETER]-B
E
|
GND>--------------+


The meter will now be indicating the base current (Ib) and all
that's left to do is to calculate Hfe:


Ic
Hfe = ----
Ib


and, from the transistor's data sheet, to determine whether the
transistor is in spec or not.

 

[Meat Plow]

Nip down to Maplin and get a meter with a transistor tester.

While a normal meter can test go or no go it cant test HFE problems.

---
Sure it can. (View in Courier):


1.

+V>-+-----+-------+
| | |
[1M]<--+ [AMMETER]
| |
| C
+-----------B
E
|
GND>--------------+


Starting with the pot cranked to maximum resistance, rotate it so
that some convenient current (Ic) is displayed by the ammeter then,
without disturbing the setting of the pot, disconnect the meter from
the collector, place it in series with the base, and connect the
collector to +V:


+V>-+-----+-------+
| | |
[1M]<--+ |
| |
| C
+-[AMMETER]-B
E
|
GND>--------------+


The meter will now be indicating the base current (Ib) and all
that's left to do is to calculate Hfe:


Ic
Hfe = ----
Ib


and, from the transistor's data sheet, to determine whether the
transistor is in spec or not.

That's fine and dandy but the OP didn't even know what symbol represented
a diode check on his vom. And this has been a teaching thread for him. I
know you have a need to right wrongs, just keep it out of this thread so
it doesn't turn into the usual argument.

 

[John Fields]

The only diode check type conduction in a bipolar transistor should be
between the base and emitter.

---
That's not true.

Matter of fact, the way to determine which lead is the base of a
transistor with an unknown pinout is to find the lead which
diode-conducts to the other two leads.

 

[John Fields]

Nip down to Maplin and get a meter with a transistor tester.

While a normal meter can test go or no go it cant test HFE problems.

---
Sure it can. (View in Courier):


1.

+V>-+-----+-------+
| | |
[1M]<--+ [AMMETER]
| |
| C
+-----------B
E
|
GND>--------------+


Starting with the pot cranked to maximum resistance, rotate it so
that some convenient current (Ic) is displayed by the ammeter then,
without disturbing the setting of the pot, disconnect the meter from
the collector, place it in series with the base, and connect the
collector to +V:


+V>-+-----+-------+
| | |
[1M]<--+ |
| |
| C
+-[AMMETER]-B
E
|
GND>--------------+


The meter will now be indicating the base current (Ib) and all
that's left to do is to calculate Hfe:


Ic
Hfe = ----
Ib


and, from the transistor's data sheet, to determine whether the
transistor is in spec or not.

That's fine and dandy but the OP didn't even know what symbol represented
a diode check on his vom. And this has been a teaching thread for him. I
know you have a need to right wrongs, just keep it out of this thread so
it doesn't turn into the usual argument.

---
Geez, Plowie, everything was going along fine until you decided to
open up that big fucking mouth of yours and criticize what didn't
need criticizing. I guess (according to you) that I should have
started another thread and referenced it to this one just to keep
from offending your delicate sensibilities about what's allowed in
the thread, ya fuckin' Nazi.

 

[John Fields]

Thanks to everyone who has replied. I am really struggling as you can see.
I can't believe that all my new BC548B transistors are broken.

Does this seem correct?

C = 4.98V
B = 1183mV

With E emitting 615mV

Does not appear to amplifying anything to me? What could I have done wrong?

---
Any number of things.

What did you do to obtain those readings?

That is, what was connected to what when you got the various
readings?

 

[Meat Plow]

On Sun, 10 Jun 2007 09:40:38 -0700, Marra

Nip down to Maplin and get a meter with a transistor tester.

While a normal meter can test go or no go it cant test HFE problems.

---
Sure it can. (View in Courier):


1.

+V>-+-----+-------+
| | |
[1M]<--+ [AMMETER]
| |
| C
+-----------B
E
|
GND>--------------+


Starting with the pot cranked to maximum resistance, rotate it so
that some convenient current (Ic) is displayed by the ammeter then,
without disturbing the setting of the pot, disconnect the meter from
the collector, place it in series with the base, and connect the
collector to +V:


+V>-+-----+-------+
| | |
[1M]<--+ |
| |
| C
+-[AMMETER]-B
E
|
GND>--------------+


The meter will now be indicating the base current (Ib) and all
that's left to do is to calculate Hfe:


Ic
Hfe = ----
Ib


and, from the transistor's data sheet, to determine whether the
transistor is in spec or not.

That's fine and dandy but the OP didn't even know what symbol represented
a diode check on his vom. And this has been a teaching thread for him. I
know you have a need to right wrongs, just keep it out of this thread so
it doesn't turn into the usual argument.

---
Geez, Plowie, everything was going along fine until you decided to
open up that big fucking mouth of yours and criticize what didn't
need criticizing. I guess (according to you) that I should have
started another thread and referenced it to this one just to keep
from offending your delicate sensibilities about what's allowed in
the thread, ya fuckin' Nazi.

As if by magic, you've proven my point.

bye

plonk

 

[John Fields]

On Sun, 10 Jun 2007 12:57:59 -0500, John Fields wrote:

On Sun, 10 Jun 2007 09:40:38 -0700, Marra

Nip down to Maplin and get a meter with a transistor tester.

While a normal meter can test go or no go it cant test HFE problems.

---
Sure it can. (View in Courier):


1.

+V>-+-----+-------+
| | |
[1M]<--+ [AMMETER]
| |
| C
+-----------B
E
|
GND>--------------+


Starting with the pot cranked to maximum resistance, rotate it so
that some convenient current (Ic) is displayed by the ammeter then,
without disturbing the setting of the pot, disconnect the meter from
the collector, place it in series with the base, and connect the
collector to +V:


+V>-+-----+-------+
| | |
[1M]<--+ |
| |
| C
+-[AMMETER]-B
E
|
GND>--------------+


The meter will now be indicating the base current (Ib) and all
that's left to do is to calculate Hfe:


Ic
Hfe = ----
Ib


and, from the transistor's data sheet, to determine whether the
transistor is in spec or not.

That's fine and dandy but the OP didn't even know what symbol represented
a diode check on his vom. And this has been a teaching thread for him. I
know you have a need to right wrongs, just keep it out of this thread so
it doesn't turn into the usual argument.

---
Geez, Plowie, everything was going along fine until you decided to
open up that big fucking mouth of yours and criticize what didn't
need criticizing. I guess (according to you) that I should have
started another thread and referenced it to this one just to keep
from offending your delicate sensibilities about what's allowed in
the thread, ya fuckin' Nazi.

As if by magic, you've proven my point.

bye

plonk

 

[Eeyore]

I'd say what was proven was that you're a loudmouthed troublemaker.

And you are ?

How many posts in s.e.b does it take to explain how to test a transistor ?

Graham

 

[John Fields]

And you are ?

---
Generally a truly helpful poster.

However, when it comes to dealing with snotty-assed shit like you I
have no compunctions at all about slapping you around and treating
you the way you treat other people.

 

[Meat Plow]

And you are ?

John is screaming into my kill filter, wonderful

How many posts in s.e.b does it take to explain how to test a transistor ?

Took four posts just to show the OP that his meter had a diode check
function.

 

[John Fields]

John is screaming into my kill filter, wonderful

---
Hardly screaming, but it got through, didn't it?
---

Took four posts just to show the OP that his meter had a diode check
function.

---
But only one to correct another poster's error and show him (the OP)
how to test for beta with a milliammeter.

Also, I see you haven't responded to my correction of your statement
that the only diode-like junction in a bipolar transistor is the
base-emitter junction.

Oh, well, since you plonked me I guess you won't be reading this...

 

[The Phantom]

The only diode check type conduction in a bipolar transistor should be
between the base and emitter.

This is not true, as can be easily verified by experiment.

 

[neon]

with any meter you can check if the transistor is good or bad. but it will not tell you how good or how bad it is. transistors are two diodes connected at the common base.so from base to emiter you are checking for a diode continuity as ohms from base to collector is another diode continuity now the meter leads voltage polarity must be known to determine if it is NPN-PNP MEANING NEG-POS,NEG. final check is emiter to collector for short. there you got it all.

 

[Ross Herbert]

Go here and scroll down to types.

http://en.wikipedia.org/wiki/Transistor

The testing data you have combined with the wiki data should help make
clearer how to determine what is the emitter and collector from your meter
readings. Your red lead should be on the base for an NPN and will conduct
with the emitter and not the collector much like a diode.

Have fun.

Not if he is using his analogue (moving coil) meter. In this case the
BLACK lead will be putting out +ve and when placed on the base of the
NPN transistor it will bias each diode ON when the RED lead is on
either of the other 2 terminals (assuming the transistor is ok).

 

[Meat Plow]

Not if he is using his analogue (moving coil) meter. In this case the
BLACK lead will be putting out +ve and when placed on the base of the
NPN transistor it will bias each diode ON when the RED lead is on
either of the other 2 terminals (assuming the transistor is ok).

Ok dammit Now I have to go dig up a transistor because this is not how
I remember it.

--
#1 Offishul Ruiner of Usenet, March 2007
#1 Usenet Asshole, March 2007
#1 Bartlo Pset, March 13-24 2007
#10 Most hated Usenetizen of all time
#8 AUK Hate Machine Cog
Pierre Salinger Memorial Hook, Line & Sinker, June 2004
COOSN-266-06-25794

 

[John Fields]

---
<JF> Not true.

An NPN looks like this: (View in Courier)


+-->|--C
|
B--+
|
+-->|--C

and a PNP like this:


+--|<--C
|
B--+
|
+--|<--C

Not if he is using his analogue (moving coil) meter. In this case the
BLACK lead will be putting out +ve

....

---
Not necessarily true; it depends on the meter.

For example, see page 20 of:

http://www.triplett.com/man/84-704.pdf

 

[John Fields]

For example, see page 20 of:

http://www.triplett.com/man/84-704.pdf

 

[Clint Sharp]

Ok dammit Now I have to go dig up a transistor because this is not how
I remember it.

That is correct with *most* analogue meters but I have had high
impedance (FET buffered) analogue meters that don't behave that way.